The present invention relates to a method of fixing an optical element such as a plastic lens, as well as to an optical component and an optical pickup on which an optical element such as an objective lens has been mounted using the fixing method.
Many types of pickups for playing back and recording data on an optical disc including CD (compact disc), DVD (digital versatile disc) and BD (Blu-ray disc) have been developed and manufactured (see Patent Document 1). As an objective lens mounted in these optical pickups, plastic lenses have frequently been employed because of their light weight, and making for precious focusing and tracking. A plastic objective lenses like the above is bonded and fixed on a bobbin, which is a moving part of the optical pickup, using resin adhesive for example.
[Patent Document 1] Tokkai No. Hei 10-162407
In the mass-production process of optical pickups for CDs and DVDs currently available on the market, a UV hardening type of adhesive is mostly employed for fixing objective lenses in order to ensure a speedy manufacturing process. However, if the same techniques are applied to mass-production process of optical pickups for BDs which utilize shorter wavelengths, the problems below become evident.
That is, it was found through experiments by the inventor of this invention that, because an intense UV light beam is irradiated onto the entire plastic objective lens while curing the UV hardening type of adhesive, the transmission characteristics related to blue light and ultraviolet light, which are supposed to be utilized on the mounted lens, are deteriorated for some specific types of plastic objective lenses. Deterioration of the transmission characteristics of plastic objective lenses due to irradiation of an intense UV light beam has not caused any problems because most plastic objective lenses have conventionally been utilized in the region of infrared or visible long wavelengths.
However, if a UV hardening type of adhesive is employed for mounting plastic objective lenses in the mass-production process of new type optical pickups which utilize blue light or ultraviolet light for recording and play back, the transmission characteristics related to blue light and ultraviolet light deteriorate which are utilized by the mounted plastic objective lens as above, and which results in problems in that the recording and playing accuracy of data is lowered, and further the expected performance may not be achieved.
Accordingly, an object of the present invention is to offer a method of fixing an optical element, such as a plastic objective lens in which deterioration of transmission characteristics can be reduced in the working wavelength range of the optical element in the case the optical element is fixed by using a UV hardening type of adhesive.
Another object of the present invention is to offer an optical component equipped with an optical element that has been fixed by using the above fixing method, as well as an optical pickup containing the optical component.